Secretary of State John Kerry is back in Washington. He's just finished a marathon trip through the Middle East, including a near miss in negotiations with Iran over its nuclear program. Kerry's task now is to defend the diplomatic position he staked out in those negotiations so far. And tomorrow, he'll meet with lawmakers and urge them to hold off on new sanctions to give the talks a chance. But, as NPR's Michele Kelemen reports, that is a tough sell.

MICHELE KELEMEN, BYLINE: The chairman of the Senate Foreign Relations Committee, New Jersey Democrat Robert Menendez, has a lot of questions for Kerry about the interim deal diplomats are offering to Tehran.

SENATOR ROBERT MENENDEZ: I am concerned that we seem to be more desirous of a deal than the Iranians, who clearly need a deal. The Iranian economy is in a tailspin. The sanctions have really worked.

KELEMEN: Menendez doesn't want to let up the pressure now. He says it takes time to put new sanctions in place and they can be drawn up in a way that would depend on the outcome of talks.

MENENDEZ: It would be both an insurance policy for the United States, just in case Iran, based upon past history, doesn't come through with an agreement, and/or an incentive to the Iranians to actually strike an agreement.

KELEMEN: The New Jersey Democrat is skeptical about the diplomacy as long as Iran continues to enrich uranium and develop a heavy water reactor that could give Tehran a plutonium path to a bomb. He says it seems the French were the ones who raised those issues with the other permanent Security Council members plus Germany.

MENENDEZ: If the French are playing that role, I applaud them because from my perspective, you need individuals within the P5+1 that will drive the bargain to where it needs to be in order to create a global security against a nuclear weapons program by Iran.

KELEMEN: That French position has been useful for the U.S. diplomatically for some time now, says Karim Sadjadpour of the Carnegie Endowment for International Peace.

KARIM SADJADPOUR: For the last several years, the French have been to America's right when it comes to Iran's nuclear program. They are very serious when it comes to nonproliferation issues and they have a deep understanding of Iran.

KELEMEN: Secretary Kerry says while the French have been more vocal about some things, he insists the U.S. and all of its partners were united on their proposal to Iran. Iran's foreign minister says in a tweet that no amount of spin can change what happened. He suggested France gutted a U.S. draft. Former ambassador John Limbert says the Americans are starting to look more reasonable than the French.

JOHN LIMBERT: The joke in Tehran now is they're going to take the French embassy and give it to the Americans.

KELEMEN: Limbert was one of the U.S. diplomats held hostage by Iran after the revolution there and he worked on Iran for the Obama administration. Now a professor at the Naval Academy, Limbert says it will be difficult to close a deal that allays everyone's concerns and suspicions. But he's been surprised by the pace of negotiations.

LIMBERT: You couldn't even dream of something like this happening. You know, the fact that the secretary of State would have, like, six or seven hours of one-on-one meetings with his Iranian counterpart, it was unimaginable. We are engaged with the Iranians, like it or not, at a level we haven't been for 34 years.

KELEMEN: For the first time in decades, he says, U.S. and Iranian officials are talking to each other rather than yelling. The Carnegie Endowment's Sadjadpour also sees it as a positive sign that Iran's foreign minister took to Twitter to explain his view of why talks have failed so far.

SADJADPOUR: If we can coin a new theory of international relations, it's that countries that tweet at one another are less likely to go to war against one another. To paraphrase Winston Churchill, tweet tweet is better than war war.

KELEMEN: Talks are to continue at a lower level later this month in Geneva. Michele Kelemen, NPR News, Washington. Transcript provided by NPR, Copyright NPR.